In the interest of interoperability of wireless communications equipment and devices, there has been a considerable amount of effort expended between various global standards bodies to establish a single direct sequence (DS) code-division multiple access (CDMA) communications system that may be used throughout the world. Unfortunately, despite all of the work, there has been seen an emergence of two dominant standards for frequency division duplex (FDD) single carrier CDMA for use in third generation networks, named CDMA2000 (also referred to as IS-2000) and UMTS WCDMA (Universal Mobile Telephony System Wideband-CDMA, commonly referred to as UMTS).
While these two technical standards are both based upon CDMA, they are basically incompatible. This means that a CDMA2000 wireless device will not operate in a UMTS network and vice versa. Therefore, to support interoperability, a wireless device needs to be able to operate in the two incompatible networks.
One commonly used prior art technique to enable multi-network operation is to include needed hardware and software to permit operation in multiple networks. This may require the presence of multiple iterations of certain hardware components within a single wireless device. The repeated hardware and software components may range from analog signal processing components if the operating frequencies of the networks are different to specific digital components such as correlators and so forth if differences in the networks are relatively smaller and lie mainly in the encoding of the transmitted signals.
For example, CDMA2000 and UMTS networks are both based upon CDMA. However, the two standards differ in many respects, including but not limited to chip-rate (1.2288 MHz vs. 3.84 MHz), frame length, scrambling code (augmented PN codes vs. Gold codes), transmit diversity (OTD or STS vs. STTD), and separation of base-station codes (phase offsets vs. unique Gold codes). For detailed explanation of the differences between CDMA2000 and UMTS, refer to technical documentation for the two standards. The differences between CDMA2000 and UMTS (some of which are listed above) may require different designs for various hardware and software components, especially the searcher units, which are used in the synchronization of the wireless devices to the network equipment (namely, base stations). Network synchronization is an especially critical for proper operation in CDMA2000 and UMTS, since a wireless device is required to become synchronized with the wireless communications network in order to communicate.
One disadvantage of the prior art is that the inclusion of multiple iterations of hardware and software components to support operation in multiple networks may consume more resources, such as memory and integrated circuit real-estate. This can result in a larger and more expensive wireless device.
A second disadvantage of the prior art is that the use of multiple hardware components in a single wireless device can increase power consumption, resulting in shorter battery life or requiring the use of more expensive batteries and/or battery technology.
A third disadvantage of the prior art is that the presence of multiple hardware and software components in a single wireless device may help to reduce the reliability of the wireless device. The reduced reliability may come as a result of the greater amount of hardware, hence more devices that may fail. Alternatively, the reduced reliability may be the result of the greater amount of software, increasing the probability of an undiscovered bug being present in the software.